Recently my 2004 S-Type began downshifting rough into 1st gear, which eventually caused a check engine light. I had the car tested and it appears that three cylinders are misfiring. I replaced all 6 spark plugs, but that didn't solve the problem. (Didn't really think it would!) But it has also been speculated that given the symptoms which are jumping, loss of power, and a bouncing tachometer when accelerating, that it could be the spark plug coils causing the misfire. Anyone ever run into this problem? Thanks for your help!

 

Please tell us; V8 or V6 car (may help to add a signature to your profile with that information)

Also, do you have a list of actual codes from when the car was "checked".

If a V6, was the 3 missing cylinders on one bank (side)?

When it is down on power and you try accelerating, does it hesitate or buck and trip the "restricted performance" light?

 

Much more likely to be coils but also could be an air leak or pwoer or ...

Yes, more car details needed!

 

Yes its the 3.0 V6 and it's missing on both banks, two on the left, one on the right. The "restricted performance" light is on as well. There is a great amount of hesitation when stepping on the gas met with an inconsistent RPM at around 40Mph, but goes away at about 50.

Engine error codes

P0300
P0301
P1316
P1111
P0174
P0171

Hope this helps!

 

John, It's all yours. I'm at lunch at work and don't have my handy dandy OBDII code list...

But, don't think it's what I thought it might be....

 

Any chance to read the LTFTs (long term fuel trims)? If so, at idle and about 2500rpm (in P or N).

You're looking to see whether both banks are similar, whether they're more than about 5 or 10% and whether they head much lower (towards 0) at higher revs. But just post raw values if you can.

Otherwise I guess replace #1 coil (see the P0301) and see what happens next.

BTW, the codes PDF is in the FAQs (as well as JTIS)

 

Thanks for the answers guys!

I'll start with this and see what it does. Seems to me that all signs point to the coils. I'll repost with an update!

73's